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Infectious Mononucleosis

What is infectious mononucleosis?

Infectious mononucleosis is characterized by swollen lymph glands, fever, sore throat, and extreme fatigue. It’s often spread through contact with infected saliva from the mouth. Symptoms can take between 4 to 6 weeks to appear and usually do not last beyond 4 months. Transmission is impossible to prevent because even symptom-free people can carry the virus in their saliva.

What causes infectious mononucleosis?

Infectious mononucleosis is caused by the Epstein-Barr virus (EBV). A variant of mononucleosis that is milder than EBV infectious mononucleosis is caused by the cytomegalovirus (CMV). Both EBV and CMV are members of the herpes virus family:

In the U.S., most adults between 35 and 40 years old have been infected with the Epstein-Barr virus. This is a very common virus. When children are infected with the virus, they usually do not experience any noticeable symptoms. However, uninfected adolescents and young adults who come in contact with the virus may develop an illness very similar to infectious mononucleosis.

The Epstein-Barr virus (EBV) may cause infectious mononucleosis in adolescents and young adults. However, even after the symptoms of infectious mononucleosis have disappeared, the EBV will remain dormant in the throat and blood cells during that person's lifetime. The virus can reactivate periodically, however, usually without symptoms.

What are the symptoms of infectious mononucleosis?

Mononucleosis usually lasts for 1 to 2 months. The following are the most common symptoms of mononucleosis. However, each person may experience symptoms differently. Symptoms may include:

Fever

Swollen lymph glands in the neck, armpits, and groin

Extreme fatigue

Sore throat

Enlarged spleen

Head and body aches

Liver involvement, such as mild liver damage that can cause temporary jaundice, a yellow discoloration of the skin and whites of the eyes due to abnormally high levels of bilirubin (bile pigmentation) in the bloodstream

Once a person has had mononucleosis, the virus remains dormant in the throat and blood cells for the rest of that person's life. Once a person has been exposed to the Epstein-Barr virus, a person is usually not at risk for developing mononucleosis again.

The symptoms of mononucleosis may resemble other medical conditions. Always talk with your healthcare provider for a diagnosis.

How is infectious mononucleosis diagnosed?

A diagnosis of mononucleosis is usually based on reported symptoms. However, diagnosis can be confirmed with specific blood tests and other lab tests, including:

White blood cell count, which is not diagnostic, but the presence of certain types of white blood cells (lymphocytes) may support the diagnosis